As high resolution and large screen in a plasma display panel (hereinafter, referred to as ‘PDP’) are realized, a 65-inch television and the like are produced commercially. In recent years, application of a PDP to full spec Hi-Vision, in which the number of scan lines is twice or more than that in the known NTSC system, is under progress and a PDP not containing lead is requested in consideration of an environmental issue.
Basically, a PDP is configured to include a front plate and a rear plate. The front panel is configured to include a glass substrate made of sodium borosilicate based glass using a float method, display electrodes including strip-shaped transparent electrodes and bus electrodes formed on a main surface of the glass substrate, a dielectric layer that covers the display electrodes and serves as a capacitor, and a protective layer that is formed on the dielectric layer and made of magnesium oxide (MgO). On the other hand, the rear plate is configured to include a glass substrate, strip-shaped address electrodes formed on a main surface of the glass substrate, a base dielectric layer that covers the address electrodes, barrier ribs formed on the base dielectric layer, and a phosphor layer that is formed between the barrier ribs to emit light in red, green, and blue colors.
The front plate and the rear plate are airtight sealed such that surfaces, on which electrodes are formed, of the front plate and the rear plate are disposed opposite to each other. Discharge gas of Ne—Xe is filled into a discharge space divided by barrier ribs at the pressure of 53200 Pa to 79800 Pa. In the PDP, electrical discharge occurs by selectively applying a video signal voltage to a display electrode and ultraviolet rays generated by the discharge excite each color phosphor layer to emit red, green, and blue colored light, and thus color image display is realized.
A silver electrode is used as the metal bus electrode of the display electrode in order to secure the conductivity and a low-melting-point glass material having lead oxide as a main component is used for the dielectric layer. However, in consideration of an environmental issue in recent years, an example not containing a lead component as the dielectric layer is disclosed (for example, refer to Patent Documents 1, 2, and 3).
Moreover, in recent years, application of a PDP to full spec Hi-Vision, in which the number of scan lines is twice or more than that in the known NTSC system, is under progress. Due to such application to Hi-Vision, the number of scan lines increases, and accordingly, the number of display electrodes increases. As a result, a distance between display electrodes becomes further reduced.
For this reason, silver ions are more diffused from silver electrodes, which form display electrodes, to a dielectric layer. If silver ions are diffused into the dielectric layer, the silver ions are reduced by alkali metal ions contained in the dielectric layer, thereby forming colloidal silver oxide. Due to the silver oxide, the dielectric layer is strongly colored in yellow or brown. In addition, a part of the silver oxide is reduced to generate oxygen bubbles, and the bubbles cause poor insulation.
Therefore, it has been proposed to use a low-melting-point glass material such as bismuth oxide, which serves to inhibit reaction with a silver electrode, for the dielectric layer without allowing a lead component to be contained in the dielectric layer; however, it has been difficult to properly set the thickness of the dielectric layer, which uses the low-melting-point glass material such as bismuth oxide, with respect to the thickness of the display electrode having the silver electrode. That is, if the thickness of the dielectric layer is smaller than the thickness of the display electrode, the low-melting-point glass material such as bismuth oxide is smaller than the silver electrode, and accordingly, an effect of inhibiting reaction with the silver electrode is reduced. In contrast , if the thickness of the dielectric layer is larger than the thickness of the display electrode, the low-melting-point glass material such as bismuth oxide serves to inhibit the reaction with the silver electrode, but it is difficult that bubbles generated due to generated silver oxide escape from the dielectric layer, resulting in a cause of poor insulation.
Thus, in the known dielectric layer not containing a lead component, which has been suggested in consideration of the environmental issue, it has been difficult to properly set the thickness of the dielectric layer with respect to the thickness of the display electrode.
[Patent Document 1] Japanese Patent Unexamined Publication No. 2003-128430
[Patent Document 2] Japanese Patent Unexamined Publication No. 2002-053342
[Patent Document 3] Japanese Patent Unexamined Publication No. 9-050769